Scientists in the US are worried over the increasing malfunction of heart devices, which they say were directly responsible for 61 deaths between 1990 and 2002.
The Food and Drug Administration (FDA) released a study at a meeting with physicians and heart-device manufacturers recently, which found that 4,225 defibrillators had failed between 2000 and 2003. Same number of defibrillators failed in the previous 10 years, reports online edition of The Washington Post.
Overall, the failure rate of the devices was significantly higher in the second half of the period studied than in the first half, it said.
William H. Maisel, the Harvard Medical School physician who conducted the study, said the increase is significant and contrasts with a consistent decline in the rate at which pacemakers have to be removed.
The higher percentage of failures may be a result of design changes that made the devices smaller - they are now the size of a stopwatch - while their computer memory was increased and their power maintained, it said.
Scott Gottlieb, the FDA's deputy commissioner for policy, said the study's results and other agency data are disturbing, although the devices remain lifesavers for several million people.
"When we looked across the annual reports we receive about these products, we have found some increasing trends for certain kinds of problems with some devices," he was quoted as saying in the meeting.
"This happened even as these devices got smaller, more sophisticated and more robust in their lifesaving benefits."
According to the Heart Rhythm Society, as many as 175,000 Americans are likely to get defibrillators implanted this year. Their usage has expanded even as serious questions have been raised about the dependability of some models.
One of the biggest defibrillator makers, Guidant Corp., recalled 109,000 implantable devices in June after finding they could develop an internal short circuit without warning, resulting in a failure to deliver a shock when needed.
The FDA has advised patients to discuss with their doctors the advisability of replacing their defibrillators. But, a number of physicians said they do not have all the information they need to make those decisions.